Set BOARD_SYSTEMSDK_VERSIONS even if PRODUCT_SHIPPING_API_LEVEL is unset

Previously, we checked if PRODUCT_SHIPPING_API_LEVEL >= 28, but that no
longer is needed because upgrading from 29 to 35 is not expected. All
devices running Android V are expected to be shipped after 28.

Furthermore, this fixes non-device targets (like sdk) where
PRODUCT_SHIPPING_API_LEVEL is unset.

Bug: 318634417
Test: build with sdk target
Change-Id: I8f8337fb76312334777e621ae5870d953167ad49
diff --git a/core/config.mk b/core/config.mk
index 4d79e2b..469be30 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -831,14 +831,10 @@
 # Set BOARD_SYSTEMSDK_VERSIONS to the latest SystemSDK version starting from P-launching
 # devices if unset.
 ifndef BOARD_SYSTEMSDK_VERSIONS
-  ifdef PRODUCT_SHIPPING_API_LEVEL
-  ifneq ($(call math_gt_or_eq,$(PRODUCT_SHIPPING_API_LEVEL),28),)
-    ifeq (REL,$(PLATFORM_VERSION_CODENAME))
-      BOARD_SYSTEMSDK_VERSIONS := $(PLATFORM_SDK_VERSION)
-    else
-      BOARD_SYSTEMSDK_VERSIONS := $(PLATFORM_VERSION_CODENAME)
-    endif
-  endif
+  ifeq (REL,$(PLATFORM_VERSION_CODENAME))
+    BOARD_SYSTEMSDK_VERSIONS := $(PLATFORM_SDK_VERSION)
+  else
+    BOARD_SYSTEMSDK_VERSIONS := $(PLATFORM_VERSION_CODENAME)
   endif
 endif